This invention relates to the heating of various grains, nuts or seeds by microwave energy and has particular reference to appliances for making popcorn or the like within a microwave oven.
It is commonly known that heat may be applied to grains, nuts or seeds for various purposes. Edible nuts may be roasted, rice grains may be puffed and popcorn kernels may be popped by application of heat either radiatively or convectively in well known conventional ovens fueled by electrical energy, by the burning of liquid or gaseous fuel or by combustion of solid fuel.
Popcorn has been made in many ways. Kernels have been placed in a screenlike container with a long handle so that the container may be held suspended above an open flame. Since the heat from the flame usually radiates onto or contacts only one side of the supply of kernels, it was necessary to vigorously shake the container so that all the kernels would be heated and to prevent burning of the popped corn. Another method was to place a supply of kernels in a covered pan disposed on a burner of a kitchen range, for example, and again shake the pan to properly heat all the kernels and agitate the popped corn. Still another method has been to place the kernels in an enclosure having wall areas containing electrical heating elements. This method again usually requires that the enclosure be at least slightly agitated. In all of these methods, butter and salt must be subsequently added.
It is also known that a partially collapsed sealed foil-like disposable container may be provided with a supply of kernels and oil and agitated over a source of heat whereupon the kernels will pop, causing the container to expand, following which the container may be ruptured to remove the popcorn which will be at least partially covered with the oil. In a still further known method, a partially collapsed, sealed plastic bag of kernels, with or without oil, is placed in a microwave oven. Microwave radiation is then directed through the oven to the kernels, causing them to pop. Agitation in such a case is not necessary since microwave radiation will easily contact each kernel. A suitable oil may also be provided in this type of device.
It has been found that butter can not be used with the packaged systems because butter can become rancid after a period of time such as might occur when the packages are stored or on store shelves for a lengthy period.